Idle Surge - 426ci 2.9 Whipple

[06300CSRT8]

So been dealing with this for a very long time now, with help from the top dogs of the tuning world. Running out of ideas here, not aware of any mechanical issues, at least that could be found. The main issue is when coming to a stop in gear, or when in reverse and the lightest bit of throttle applied, it gets into a HUGE surge going from 200-1300rpms in a continuous cycle. Attached is the original tune after WOT and in gear idle was dialed in. This log shows the most obvious surging, but this log was with the PT and minimum timing tables raised up a bit, but made zero difference. Honestly after 22 revisions, we have only managed to make it worse than the tune attached. Here is what was tried with zero impact to the surging:

-Torque modifiers cut in half, then completely zero'd out as a test, only made the issue worse both ways
-modifications made to injector flow
-Cut VE by 10-15% (even though trims were adding fuel), zero difference
-I have made tons of attempts at modifying the spark tables, raising the timing def helped the cruising surge from 1200-1800 rpms (fluctuates 100rpms) but made no real change to the big surging I get when coming to a stop

I have def narrowed the problem to something relating to the throttle correlation, I THINK. Here is why, if sitting in park, I apply say 5% throttle and hold the pedal perfectly still, the RPMs rise to 1200-1300 rpms then IMMEDIATELY get pulled down and brought to near stall, then jump back up to 1200 and will continue to do this cycle, even though the pedal is EXACTLY still.

Other observations of note, the tune USED to surge all the time, in park/neutral, basically at anytime at idle, so I am convinced since the in park idle has been 95% fixed this still remains a tune issue. I am seeing some pretty big value differences of SENSED MAP and READ MAP while datalogging with DS. Don't think that's normal. If you look carefully in the log attached, there are times where the commanded torque can go really negative or just flat lines at 32ft/lbs for the entire surge cycle. In the log the first surge cycle was after putting it in reverse, and lightly touching the throttle while holding the brake, but then letting off the throttle and letting it just sit there.

2006 300C NGC CAN REV15A PT Timing 2.hpl
2006 Chrysler 300C NGC3 CAN No TCM Rev15.hpt

Full mod list:
426ci low comp 6.1L based stroker (9:1)
HHP stage 2 heads, cnc + hand ported
2.9 whipple, 2.75" blower pulley, 17% OD crank pulley, seeing 15-16psi
Custom Cam: 239/251 duration, 600 lift, 118+2 ICL
SHR trans, Getrag 3.06 rear, stock height wheel/tire combo
3 BAR MAP sensor
87mm Modern Muscle stock ported Throttle body (have switch to stock to see if this was the issue, no change to surging)

[06300CSRT8]

In the log at time 08:18:14.3, 00:01:05.08 time frame, which is right when I put it in reverse and tapped the throttle, the required torque is 181 lbft, which seems awfully high, and it also is calculating almost triple the total airflow than a split second prior of 6lb/min vs the normal 2lb/min.

[Monzsta]

Does the Whipple have a bypass valve, and is it staying open or closing during the surge event? It looks like boost surge. On some turbo cars I used to deal with we had to trim the blowoff valve springs to make the valves to hang open at idle to get them to calm down. Otherwise they'd be into surge city. Also it's seeing quite a bit of timing variation as well. This alone will cause surge oscillation. When I megasquirted an ls1 I found I really had to dumb down the timing around the idle cells to ~10 degrees or so or it'd be off and surging. Some engines are very sensitive to timing variations.

[06300CSRT8]

Have verified the bypass is staying fully open, it only "twitches" slightly when rpms fall REALLY low, aka 200-300rpms area as the vacuum actually starts to get so low it stops keeping it open. I agree though, if I showed you a video it sounds like an old Weiand blower on top of a chevy 455 with no bypass.

I really do think it comes down to timing but just cant seem to find the right changes to the various tables to get it to be more consistent. There is a PT Base, MBT, WOT, Min Spark, and then of course ALL the myriad of idle torque modifiers (proportional, integral, and derivative). The biggest change thus far between when it used to surge even in park/neutral was bringing the min spark table from -5* in most idle cells to +5* in most. I took that further and brought the miminum spark, PT spark tables all close to 10-12* and then it start to hunt for idle in park/neutral again.

[DXB_Tuner]

Try changing the spark retard (TqMgt Retard) comes under TqMgt-Engine and see what will happen.

[06300CSRT8]

Try changing the spark retard (TqMgt Retard) comes under TqMgt-Engine and see what will happen.

Think I found it, what is a good starting point to change it, cut the values in half? Are these spark or torque (nm) values?

[06300CSRT8]

Cut the values in half, and park/neutral became unstable, hunting around 700-1000rpms. Set all values to zero and got even worse.

[vortec]

From what I have personally noticed is,if you zero or reduce the TQMGT Spark Retard,the idle will hunt and or surge as there is no longer over and under speed spark control.
Hope this helps

[SultanHassanMasTuning]

dont change that makes idle all over the place.

whats your fuel trim like, also many times after market throttles are a pain

[06300CSRT8]

Trims are -3 to -5, stock throttle body is on

[06300CSRT8]

Bump back up if anyone wants to take a stab at this. Easiest way to see what is wrong is fact that in park, I put the gas to 5% the rpms climb up then IMMEDIATELY die to 3-400rpms then come back up and keeps oscillating. Something in the PCM thinks the RPM/airflow once it revs up is way to high for the given rpm and shuts the throttle body and kills the timing.

[06300CSRT8]

Here is another log, you can see the points where I apply a little gas and you can see what the rpms/timing/fueling is doing.

2006 300C NGC CAN REV15A.hpl

[Monzsta]

Take your base timing and make everything up to 1500 rpm flat at 10 degrees. Your spark timing is inducing everything. Give it a try.

Also your ltft go heavy negative, meaning the pcm is pulling fuel. This makes your throttle begin to open in an attempt to maintain idle speed. This also drop your map vacuum and puts your timing in another region altogether. Being as we can't see either your o2 sensors or your inj. pulsewith we can only speculate as to why, possibly cam overlap dilution.

This would be easy to spot on a stand alone system as your ball would be wandering all over the place on the timing and fuel maps and corrections to those cells made.

Also, your idle max rpm limit needs to be brought back to reasonable. 1500 or so. Your max idle rpm is set to 8160 rpm. edit: I was looking at a 5.7l tune. a 6.1l read has your values. nevermind.

[06300CSRT8]

There's PT, WOT, Minimum, and Torque Management Minumum tables. Which do I set flat to 10?

[Monzsta]

I'd try PT.

[06300CSRT8]

My PT table is already well above 10*, setting it there would be lowering it quite a bit. The only areas where it is less is in the 80-100kpa regions, I can raise those up but have noticed in prior attempts this made the idle less stable than more.

The fuel trims are tough to assess while in park/neutral, they are no where near those values once in gear and moving in the same pressure ratio cells. Injector pulsewidth is in my logs as a PID.

[Monzsta]

Taking out timing there would be a test to see if you can get the engine to be calm at idle, removing one of the many influencing factors. There's a huge amount of timing variation there. Taking timing out will desensitize the engine. Give it a shot at a test.

[06300CSRT8]

ok thx bud will do.

[06300CSRT8]

You sir, Monzsta, are my new best friend lol. Worked beautiful. Surge gone 90%, set all the timing to 13* (wanted more than 10*). Only issues now is an initial tip in surge, RIGHT when I touch the gas in reverse, RPMs dip 200rpms and then come right back up, but never goes into a surge. Any ideas how to dial this in the rest of the way? Been doing a lot of VE tuning now, coming along nicely.

[Monzsta]

Glad it's working for you. Now that you know what aggravates a surge you can play with it from there. Got a scan of the reverse event?